Detection and estimation of overpressures in gas reservoirs while drilling.
Ion Foidaş, Dan-Paul Ştefănescu, Ioana Vlasín
Vol. 30, no. 1 (2013), s. 87-94, 
As part of rotary - hydraulic drilling method (the most common method for drilling the wells) the rock is displaced by the action of drilling bit, being removed from the bottom and brought to the surface, through the drilling fluid. Besides this function, the drilling fluid creates a backpressure against the borehole walls, overcoming the collapse of the poorly consolidated rocks as well as the fluids influx from the formations crossed by the well.